1. Field
One or more example embodiments relate to oscillators and methods of operating oscillators.
2. Description of the Related Art
Oscillators are devices that generate signals having a regular cycle. Oscillators are used in wireless communication systems such as mobile communication terminals, satellite/radar communication devices, wireless network devices, automobile communication devices, analog sound synthesizers, etc. In one example, mobile communication devices operate in specific frequency bands, and a voltage controlled oscillator (VCO) is used to generate a specific frequency band.
Characteristics of a conventional oscillator include a quality factor, output power, and phase noise. As quality factor and output power increase, and phase noise decreases, the performance of the oscillator improves. Recently, because more highly efficient and smaller communication devices are required and operating frequency bands have increased, smaller size and larger output oscillators having higher quality factor and lower phase noise are required.
A spin torque oscillator using a spin transfer torque has recently been introduced. The spin torque oscillator may have a nanopillar structure or a point contact structure. A spin torque oscillator is relatively thin and has a relatively high quality factor compared to conventional LC oscillators and film bulk acoustic resonator oscillators.
However, in a conventional spin torque oscillator, an angle of precession of a magnetic moment (spin) is relatively small, and thus, the output power is relatively low. Also, in a conventional spin torque oscillator having a point contact structure, a critical current needed for precession is relatively high, which increases power consumption.